Method for pretreating a substrate prior to application of a polymeric coat

ABSTRACT

A method is provided for more efficient application of a polymeric coating (e.g., die coat) to a substrate (e.g., wafer) surface. One aspect of the method comprises applying an organic liquid (e.g., organic solvent) to the wafer and spinning it to coat the entire wafer surface prior to the application of die coat. This reduces surface tension on the wafer and reduces the amount of die coat required to achieve a high quality film.

FIELD OF THE INVENTION

[0001] The present invention relates in general to processing substratessuch as semiconductor wafers, and particularly to preparing asemiconductor wafer before the application of a die coat.

BACKGROUND

[0002] Both high density and lower density integrated circuits arefabricated on wafers utilizing numerous fabrication techniques,including, but not limited to, photolithography, masking, diffusion, ionimplantation, etc. After the wafers are fabricated, with the waferincluding a plurality of integrated circuit dies, a die coat is commonlyused to protect the plurality of integrated circuit dies from damageduring the remainder of the manufacturing process. It is commonly knownto use polyimides as the buffer or die coat when fabricating suchdevices or wafers.

[0003] Polyimides utilized as a spin-on die coat are somewhat expensive.Typically, conventional processes for applying a die coat require about5 grams of die coat polymer per wafer. When one considers the volume ofwafers processed over, for example, one year, this is a significantamount of material and a significant part of the cost of processing.What is needed is a way to reduce the amount of die coat polymer usedwithout significantly impacting process latitudes. One reason retainingprocess latitudes is important is because wafer-to-wafer repeatabilityis enhanced by wider process latitudes.

[0004] The goal of the coating step is to produce a generally uniform,adherent, defect-free polymeric film of desired thickness over theentire wafer. Spin coating is by far the most widely used technique toapply such films. This procedure is carried out by dispensing a liquiddie coat polymeric composition onto the wafer surface, and then rapidlyspinning the wafer until the die coat is distributed over the entirewafer surface.

[0005] The spin coating procedure begins with dispensing the polymericcomposition onto the wafer. The dispensing stage could be accomplishedby flooding the entire wafer with polymeric composition (requiring muchmore than 5 grams of material per wafer), or by dispensing a smallervolume of polymeric composition at the center of the wafer. The wafer isthen brought to a constant spin speed to distribute the compositionevenly over the wafer surface. During conventional processing, thewafers are typically subjected to an intermediate ramp spin speedfollowed by a final spin speed. Film thickness typically depends on theviscosity of the solvent-containing liquid polymeric composition and thefinal spin speed and time duration of the spin. Once the die coatpolymeric composition is distributed, edge bead removal solution isadded to the wafer and spun to remove excess die coat material from thewafer. Immediately following the application of the die coat materialand the bead removal solution, the wafer is dried or “softbaked” by aheat source such as a hotplate.

SUMMARY

[0006] The present invention provides a method for treating a substrate,such as a semiconductor wafer, with at least one organic liquid (e.g.,organic solvent) prior to depositing a polymeric coating, such as a diecoat polymer thereon. Significantly, for preferred embodiments of thepresent invention, the use of a solvent prewet (as this pretreatmentstep is referred to herein) reduces the amount of polymer (e.g., diecoat polymer) by more than about half compared to a process that doesnot use a solvent prewet. For example, this solvent prewet processachieves very good polymeric coating thickness profiles (e.g., bothwafer to wafer and across wafer), with less than about 5 grams, and morepreferably, with less than about 3 grams, and most preferably, with onlyabout 1 gram to about 2 grams, of polymeric material per standard wafer.The method of the present invention preferably results in a very cleanfilm, with good uniformity, with the use of significantly less polymer.

[0007] It has been shown that material costs can be reduced andwafer-to-wafer repeatability can be enhanced for a photoresist coatingthrough the use of a solvent prewet. In this system, a solvent isinitially spun onto a wafer followed by a photoresist composition. Thephotoresist composition, which retains essentially the same chemicalcomposition throughout processing, differs from a die coat compositionin that the die coat composition includes a “precursor” material that isconverted to a polymeric coating. For example, in typical polyimide diecoat systems, the precursor is a polyamic acid that is converted to apolyimide after a high temperature cure. Additionally, the photoresistcomposition has a very low viscosity relative to a die coat polymericcomposition. Typically, the ratio of viscosities of a die coat polymericcoating composition to a typical photoresist coating composition isabout 100:1. Furthermore, a photoresist material is removed, whereas adie coat material remains on the wafer. Thus, it is unexpected that asolvent prewet would not adversely affect the adhesion of a die coatmaterial.

[0008] In a preferred embodiment of the present invention, at least oneorganic liquid (e.g., organic solvent) is dispensed on a first majorsurface of a substrate (e.g., wafer) and spun to cover the surface priorto dispensing and spinning a die coat composition on the substratesurface. Preferably, the solvent or solvent mixture is compatible withthe polymeric (preferably, die coat) material employed in the overcoating (e.g., die coat). As used herein, the term “compatible” meansthat the organic liquid (e.g., solvent) does not interfere with theperformance properties of the polymeric material or conversion of apolymeric precursor to a polymeric material. Such properties include,for example, adhesion, film retention, etc. A preferred organic liquidfor the prewet in the present invention is one that is used in theformulation of the polymeric (preferably, die coat) composition. Theorganic liquids typically used have a relatively low vapor pressure,e.g., less than about 100 mm Hg at 20° C., although higher vaporpressure liquids can be used. The use of a compatible organic liquid(and preferably, a low vapor pressure solvent) for pre-treating thesurface in this manner helps to maintain generally equal adhesionproperties with much less surface tension. The net result is a cleanfilm coating with significant uniformity achieved using less polymericmaterial than conventional methods (without a solvent prewet step).

[0009] In one specifically preferred embodiment the present inventionprovides a method of coating a wafer including dispensing at least oneorganic solvent on a first major surface of the wafer; spinning thewafer until the solvent is distributed across the wafer surface;dispensing a die coat composition on the wafer having solvent on itssurface; and spinning the wafer until the die coat composition isdistributed across the wafer surface.

[0010] In another embodiment, a method is provided for coating asubstrate that includes dispensing at least one organic liquid on afirst major surface of the substrate; spinning the substrate until theorganic liquid is distributed across the substrate surface; dispensing apolymeric precursor composition on the substrate having organic liquidon its surface; and spinning the substrate until the polymeric precursorcomposition is distributed across the substrate surface; wherein thepolymeric precursor composition is converted to polymeric coating thatis not subsequently removed from the substrate.

[0011] In yet another embodiment, a method is provided that involvesincorporating an additional nozzle into a wafer processing machine;positioning the additional nozzle such that it is directed at the centerof a wafer held in the wafer processing machine; causing the nozzle todispense at least one organic solvent on the wafer by triggering asolenoid; spinning the wafer until the organic solvent is distributedacross the wafer surface; dispensing a die coat composition on the waferhaving organic solvent on its surface; and spinning the wafer until thedie coat is is distributed across the wafer surface.

[0012] In still another embodiment is a method that involves dispensingat least one prewet solvent on a first major surface of a wafer;spinning the wafer to distribute the prewet solvent across the wafersurface; dispensing a die coat composition comprising at least one diecoat composition solvent on the first major surface of the wafer havingat least one prewet solvent thereon; spinning the wafer to distributethe die coat composition across the wafer surface; and dispensing atleast one edge bead removal solvent on a second major surface of thewafer and the edge of the wafer to remove die coat composition presenton the second major surface and the edge of the wafer; wherein at leastone prewet solvent is the same as at least one die coat compositionsolvent and at least one edge bead removal solvent.

[0013] These and other embodiments, aspects, advantages, and features ofthe present invention will be set forth in part in the description whichfollows, and in part will become apparent to those skilled in the art byreference to the following description of the invention and referenceddrawings or by practice of the invention. The aspects, advantages, andfeatures of the invention are realized and attained by means of theinstrumentalities, procedures, and combinations particularly pointed outin the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a block diagram of a conventional solvent dispensingapparatus.

[0015]FIG. 2 is a block diagram of a semiconductor wafer processingsystem incorporating a bulk solvent system.

[0016]FIG. 3 is a block diagram of a solvent dispensing apparatus usefulin the method of the present invention.

[0017]FIG. 4 is a flow diagram describing steps of a wafer coatingmethod according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention. It is to beunderstood that other embodiments may be utilized and that changes maybe made without departing from the spirit and scope of the presentinvention. The following detailed description is, therefore, not to betaken in a limiting sense, and the scope of the present invention isdefined by the appended claims.

[0019] It is to be understood that the term substrate, as used herein,includes a wide variety of semiconductor-based structures. A substratecan be a single layer of material, such as silicon (Si) wafer. Substrateis also to be understood as including silicon-on-sapphire (SOS)technology, silicon-on-insulator (SOI) technology, doped and undopedsemiconductors, epitaxial layers of silicon (Si) supported by a basesemiconductor, as well as other semiconductor-based structures,including any number of layers as is well known to one skilled in theart. Furthermore, when reference is made to a substrate in the followingdescription, previous process steps may have been utilized to formregions/junctions in a base semiconductor structure.

[0020] Thus, in the following text the term “wafer” is intended as arepresentative reference to the substrate or base upon which anintegrated circuit device is to be constructed. The term “die coat” isintended as a representative reference to a polymeric coating (e.g.,over coating) that is not removed in subsequent processing. Preferably,the term represents any of the set of materials known and used in theart as die coats, for example, polyimides and polybenzoxazole. The term“organic solvent” is intended as a representative reference to anorganic liquid that is typically used as a solvent, particularly in adie coat composition, although it is not necessarily being used for itssolubilizing ability.

[0021] According to the present invention, a pretreatment or prewet stepis performed prior to the die coat dispense step. This pretreatment steppreferably includes dispensing organic solvent(s) onto the wafer, andthen spinning the wafer partially dry in order to spread the solventevenly over the wafer surface. Subsequently, the die coat composition isapplied. This solvent pretreatment or prewet allows the die coat to flowand evenly distribute across the wafer surface with less die coatmaterial.

[0022] The presence on the wafer surface of the solvent prior todispensing die coat polymer reduces the surface tension. As a result ofthe reduced surface tension, when a die coat composition is subsequentlydispensed, a clean coat is achieved using substantially less die coatmaterial. That is, the die coat created following the pretreatment stepof the present invention shows the same number or fewer surface defectsthan a coat created using conventional methods. As used herein, the term“clean” refers to a die coat possessing at least the same uniformity orbetter uniformity than a die coat prepared by a conventional process.The ability to obtain the same overall coat thickness as a conventionalprocess assists to maintain the same or better adhesion and photoproperties as the conventional process, and thus results in the same orbetter overall reliability of the wafer. Good film uniformity is alsoobtained using significantly less die coat polymer. Preferably, themethod of the present invention provides a wafer to wafer die coatuniformity of typically less than about 10% across the wafer andtypically less than about 5% from wafer to wafer. This ensures greaterprocess control.

[0023] Including the prewet step reduces the amount of expensive diecoat material used by at least about 50%, and often by up to about 60%.As an example, where a conventional system dispenses 5 grams of die coatpolymer per wafer, a process employing the prewet step reduces theamount of die coat polymer used to 2 grams per wafer. The reduction indie coat dispensed also reduces the amount of solvent waste, providingadditional economic and ecologic benefits. Those skilled in the art willrecognize that these examples are offered for illustration only and arenot intended to be exclusive or limiting.

[0024] For solvent prewet and die coating wafer processing using spin-oncoating techniques, timing is important in obtaining wafer-to-waferrepeatability. Mechanical requirements are also less restrictive becausethe overall process time is less with the prewet process as compared tothe conventional process. In a conventional process that does notinvolve a solvent prewet, there is an intermediate ramp speed followedby a final spin speed. With a solvent prewet, the subsequent die coatingprocess can be ramped up faster without an intermediate spin speed,although an intermediate spin speed can be used if desired. This reducesmechanical wear of the equipment.

[0025] A typical die coat composition contains at least one organicsolvent. Additionally, the die coat composition also typically containsa polymer precursor and other additives including, but not limited to,photoactive compounds, adhesion promoters, and stabilizers. In apreferred embodiment, the same solvent that is used in the die coatcomposition and/or to clean the wafer edges after the die coat has beendeposited (e.g., an edge bead removal solvent) is used in the prewetstep. This may potentially eliminate undesirable interactions that couldchange the performance of the polymer die coating material. Using thesame solvent in as many steps as possible reduces the opportunity forunexpected reactions between the materials, and also simplifies theplumbing requirements of the coating apparatus.

[0026] Preferred organic solvents for the pretreatment (prewet) of awafer prior to die coat application include those organic liquids havinga vapor pressure of less than about 100 mm Hg at 20° C. Although theseare preferred, higher vapor pressure solvents can be used as long asthey are able to form a very thin layer of solvent (preferably, amonolayer of solvent molecules) onto which the subsequent die coatpolymeric composition is spun.

[0027] A process using a low vapor pressure (i.e., low evaporation rate)solvent as a prewet, could spin the wafer for up to five seconds andstill maintain a thin layer of the solvent on the wafer. In contrast, aprocess using a high vapor pressure (i.e., high evaporation rate)solvent as a prewet would not be able to spin for as long of a time andstill maintain a thin layer of solvent on the wafer. This would resultin the wafer being completely dry and consequently no different thanconventional coating. The ability to extend the spin period for a lowvapor pressure solvent may increase the repeatability across fabricationmachines.

[0028] Examples of suitable solvents include, but are not limited to,methanol, N-methyl pyrrolidone (NMP), gamma-butyro lactone (GBL), N,N,dimethylformamide, N-butylacetate, methanol, and RER 470 (30%N-methyl-2-pyrrolidone (NMP) and 70% cyclopentanone) available from OlinHunt Corporation. Those skilled in the art will recognize that othersolvents may be used in the implementation of the present inventionwithout exceeding it's scope and spirit.

[0029] The die coat composition typically includes at least one polymerprecursor, such as polyamic acid, polyamic ester, or polybenzoxazoleprecursors. The die coat composition also contains at least one organicsolvent, such as the solvents described above. In addition to thepolymer precursor and organic solvent, additional additives may beemployed in the die coat composition. These additives include, but arenot limited to, stabilizers, adhesion promoters, photoactive compounds,surfactants, etc.

[0030] Typically, according to the present invention, the solvent isdispensed on a wafer and evenly distributed by spinning the wafer toform a very thin layer. This is typically carried out in less than abouttwo seconds at ambient temperature and pressure. Prior to evaporation, adie coat composition is dispensed onto the solvent-coated wafer andevenly distributed by spinning the wafer. This is typically carried outin less than about 30 seconds. Spinning of the wafer typically continuesfor at least about 30 seconds, and preferably no greater than about 40seconds to chemically remove the die coating from the edge and backsideof the wafer according to conventional wafer manufacturing proceduresknown in the art. The final thickness of the wafer is principallycontrolled by the overall spin process, which is typically carried outat room temperature and pressure.

[0031] As is well known to one skilled in the art, when spinning on acoating material such as polyimide coating material, the coatingmaterial is applied on the wafer surface to be coated and the wafer isthen spun such that the coating material is distributed over the waferby centrifugal force. The final thickness of the layer of coatingmaterial on the wafer is based on, at least in part, the spin rate, theviscosity of the coating material, temperature, pressure, etc. Thepreferred thickness of the die coating material applied on the wafer isin the range of about 1 micron to about 24 microns. More preferably, thethickness of the die coating material is in the range of about 5-micronsto about 15 microns.

[0032] The spinning process, for both the solvent prewet and the diecoat, can be carried out in numerous steps. For example, the solventprewet or the die coating material can be dispensed on the wafer whilethe wafer is standing still and then the speed is increased to aparticular speed for distributing the material over a period of time.Any number of intermediate spinning steps could be utilized such asgoing from stand still to an intermediate speed for a particular periodof time and then further increasing the spinning speed. It will bereadily apparent that a multitude of spinning parameters arecontemplated in accordance with the present invention as described inthe accompanying claims. The spinning process can be carried out withany number of different spin coating systems.

[0033] The methods of the present invention can use conventional trackcoating units, as shown in FIG. 1, which employ a fixed dispense head130 with a first dispense nozzle 121 for dispensing die coat directlyonto the wafer 110. The timing and flow of die coat through nozzle 121is controlled by pump 161. Pump 161 is in communication with trackcoating logic 140 by wire 151, and is triggered by binary codingcontained in the recipe executed by logic 140. Second nozzle 122dispenses solvent on the edge and sides of wafer 110 for edge beadremoval after the die coat has been spun the requisite amount of time toobtain the desired thickness. Third nozzle 123 dispenses solvent on thebackside of wafer 110 for cleaning after die coat deposition. The timingand flow of solvent through nozzles 122 and 123 is controlled bysolenoids 132 and 133, respectively. Solenoids 132 and 133 are also incommunication with track coating logic 140 via wires 152 and 153, andtriggered by binary coding contained in the recipe executed by logic140. For example, binary code of ‘1’ triggers solenoid 132 and a binarycode of ‘2’ triggers solenoid 133. A binary code of ‘3’ triggerssolenoids 132 and 133 simultaneously.

[0034] As shown in FIG. 2, solvent is held in a bulk solvent system 210external to the track coating unit 100, and connected to the trackcoating unit 100 through a low pressure canister 220. The low pressurecanister 220 maintains the proper fluid pressure and level for the trackcoating unit. The line carrying the solvent 240 connects to a dispensehead 130 within track coating unit 100. Such systems are well-known inthe art and so will not be described in further detail.

[0035] If desired, and as shown in FIG. 3, fourth nozzle 324 mayoptionally be positioned directly above wafer 110 to dispense solventprior to die coat deposition. Nozzle 324 is controlled by solenoid 334which is in communication with the track coating unit logic 140 via wire354. Solenoid 334 is activated by binary coding executed in the coatingunit logic 140.

[0036] One skilled in the art will recognize that the mechanicalportions of this improvement (containing the fourth nozzle 324 and thirdsolenoid 334) are easily integrated into conventional processingequipment. An additional binary code is also easily incorporated totrigger the fourth nozzle at the desired times. The net result is asimple-to-employ solvent dispense system which is both more reliable andmore efficient than many conventional systems, and which greatly reduceswafer processing costs.

[0037] According to one embodiment of the present invention as outlinedin the flow chart of FIG. 4, the initial step is to configure thecoating system hardware (410). According to this embodiment of thepresent invention, this step includes incorporating a fourth nozzle intothe system and positioning it such that it is directed at the center ofa wafer held in the coating system. A wafer is then mounted in thecoating system (420). Next, solvent is dispensed through the fourthnozzle onto the wafer (430). The wafer is then spun to partially dry thesolvent and spread it over the surface of the wafer (440).

[0038] Once this wafer prewet process is complete, die coat is dispensedonto the wafer (450). The wafer is again brought to spin velocity todistribute the die coat over the wafer surface (460). The solventcoating the wafer reduces friction and allows the die coat to spreadmore quickly and at least as evenly as the conventional coat. Anothereffect is less die coat material needs to be dispensed to acheiveadequate wafer coverage.

[0039] An organic solvent prewet (particularly one with low vaporpressure) ensures that a thin layer of solvent remains on the waferthroughout the die coat dispense and spin. The resulting decreasedsurface tension allows for the immediate ramp to the final spin speedwithout an intermediate step. As used herein, the “final spin speed”refers to the highest speed employed throughout the spin speed protocol.The final spin speed occurs during the thickness determining portion ofthe spin speed protocol and helps to reduce overall process time. Also,an organic solvent prewet (particularly, one with a low vapor pressure)may provide more time to spread the die coat over the wafer and moretime to bring the wafer to the proper spin velocity and stabilize it.This enables greater wafer-to-wafer consistency throughout the batch.Once the die coat spin step is complete, post-processing is performed(470). Post-processing includes activities such as edge bead removal(EBR) and heating the die coat precursor to convert it to a die coatpolymer. Those skilled in the art will recognize that the abovedescription is offered for illustration and are not intended to beexclusive or limiting.

EXAMPLE

[0040] A typical solvent prewet and die coating process can be brokendown into 15 steps as outlined below.

[0041] Step 1: Arm Positioning

[0042] Dispense arm moves to prewet position and wafer speed ramps up.

[0043] Step 2: Prewet Dispense

[0044] Dispense arm is at prewet position, wafer speed ramps up, andprewet chemical is dispensed on wafer.

[0045] Step 3: Prewet Spin Out

[0046] Arm moves to spin-on die coat dispense position, wafer speedramps up, and prewet chemical is spun out to produce monolayer film.

[0047] Step 4: Chemical Dispense

[0048] Arm is at spin-on die coat dispense position, wafer speed rampsdown, and spin-on die coat chemical is dispensed.

[0049] Step 5: Spin Out

[0050] Arm moves to home position, wafer speed ramps up, and spin-on diecoat chemical is spun out to create a uniform coating.

[0051] Steps 6-8: Cast Time

[0052] Topside EBR Arm moves to position, wafer speed ramps down,spin-on die coat is spun to desired thickness, and some solvent is driedfrom spin-on die coat.

[0053] Steps 9-11: Topside and Backside EBR

[0054] EBR Arm moves to topside position, wafer speed ramps down, andspin-on die coat is chemically removed from the edge of the wafer (frontand back).

[0055] Steps 12 and 13: EBR Dry Time

[0056] EBR Arm moves to home position, wafer speed ramps up, and spin-ondie coat continues to be removed from the back edge of wafer.

[0057] Steps 14 and 15: Finish Process

[0058] Spindle moves to top (home) position, wafer speed ramps down.

[0059] Physical Results:

[0060] The desired percentage for Across the Wafer Uniformity is lessthat about 10%.

[0061] Across Wafer Uniformity for Standard Non-solvent Prewet PolyimideProcess is 5707 angstroms (Å) or 5%, this is a 10 wafer average.

[0062] Across Wafer Uniformity for the Solvent Prewet Polyimide Processis 4371 Å.

[0063] The desired percentage for Wafer to Wafer Uniformity is less thanabout 5%.

[0064] Wafer to Wafer Uniformity for both the Standard Non-SolventPrewet Polyimide Process and the Solvent Prewet Polyimide Process isless than about 1.5%.

[0065] It is to be understood that the above description is intended tobe illustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reviewing the abovedescription. The scope of the invention should, therefore, be determinedwith reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

What is claimed is:
 1. A method of coating a wafer, comprising: dispensing at least one organic solvent on a first major surface of the wafer; spinning the wafer until the solvent is distributed across the wafer surface; dispensing a die coat composition on the wafer having solvent on its surface; and spinning the wafer until the die coat composition is distributed across the wafer surface.
 2. The method of claim 1 wherein the wafer is a silicon wafer.
 3. The method of claim 1 wherein the step of dispensing a solvent comprises dispensing a solvent having a vapor pressure of less than about 100 mm Hg at 20° C. on the wafer.
 4. The method of claim 1 wherein the step of dispensing a solvent comprises: positioning a nozzle to dispense the solvent in the middle of the wafer; controlling the nozzle with a solenoid; and causing the nozzle to dispense the solvent by signaling the solenoid.
 5. The method of claim 1 wherein the die coat composition comprises at least one polymer precursor and at least one organic solvent.
 6. The method of claim 5 wherein dispensing at least one organic solvent on the wafer comprises dispensing at least one solvent that is the same as the at least one solvent of the die coat composition.
 7. The method of claim 1 further comprising heating the die coat composition to form a polymeric die coat.
 8. The method of claim 6 wherein the polymeric die coat is used in an amount less than the amount used under the same conditions without a solvent prewet step.
 9. The method of claim 1 further comprising removing die coat composition from the edge of the wafer.
 10. The method of claim 1 further comprising removing die coat composition from a second major surface of the wafer.
 11. A method of coating a substrate, comprising: dispensing at least one organic liquid on a first major surface of the substrate; spinning the substrate until the organic liquid is distributed across the substrate surface; dispensing a polymeric precursor composition on the substrate having organic liquid on its surface; and spinning the substrate until the polymeric precursor composition is distributed across the substrate surface; wherein the polymeric precursor composition is converted to polymeric coating that is not subsequently removed from the substrate.
 12. A method of coating a wafer, comprising: incorporating an additional nozzle into a wafer processing machine; positioning the additional nozzle such that it is directed at the center of a wafer held in the wafer processing machine; causing the nozzle to dispense at least one organic solvent on the wafer by triggering a solenoid; spinning the wafer until the organic solvent is distributed across the wafer surface; dispensing a die coat composition on the wafer having organic solvent on its surface; and spinning the wafer until the die coat is distributed across the wafer surface.
 13. The method of claim 12 wherein the solvent has a vapor pressure of less than about 100 mm Hg at 20° C.
 14. A method of coating a wafer, comprising: dispensing at least one prewet solvent on a first major surface of a wafer; spinning the wafer to distribute the prewet solvent across the wafer surface; dispensing a die coat composition comprising at least one die coat composition solvent on the first major surface of the wafer having at least one prewet solvent thereon; spinning the wafer to distribute the die coat composition across the wafer surface; and dispensing at least one edge bead removal solvent on a second major surface of the wafer and the edge of the wafer to remove die coat composition present on the second major surface and the edge of the wafer; wherein at least one prewet solvent is the same as at least one die coat composition solvent and at least one edge bead removal solvent.
 15. A method of coating a substrate, comprising: dispensing at least one organic liquid on a first major surface of the substrate; spinning the substrate until the organic liquid is distributed across the substrate surface; dispensing a die coat composition on the substrate having organic liquid on its surface, wherein the die coat composition comprises at least one organic solvent; and spinning the substrate until the die coat composition is distributed across the substrate surface.
 16. The method of claim 15 wherein the die coat composition further comprises an additive selected from the group consisting of photoactive compounds, adhesion promoters, stabilizers, surfactants, and combinations thereof.
 17. The method of claim 15 wherein the die coat composition further comprises a polymer precursor selected from the group consisting of polyamic acid, polyamic ester, polybenzoxazole precursors, and combinations thereof.
 18. The method of claim 17 wherein the polymer precursor is converted to polymeric coating that is not subsequently removed from the substrate.
 19. A method of coating a substrate, comprising: dispensing at least one organic liquid on a first major surface of the substrate; spinning the substrate until the organic liquid is distributed across the substrate surface; dispensing a die coat composition on the substrate having organic liquid on its surface, wherein the die coat composition comprises an additive selected from the group consisting of photoactive compounds, adhesion promoters, stabilizers, surfactants, and combinations thereof; and spinning the substrate until the die coat composition is distributed across the substrate surface.
 20. The method of claim 19 wherein the organic liquid comprises an organic solvent.
 21. The method of claim 20 wherein the die coat composition further comprises at least one organic solvent.
 22. The method of claim 19 wherein the die coat composition further comprises a polymer precursor selected from the group consisting of polyamic acid, polyamic ester, polybenzoxazole precursors, and combinations thereof.
 23. The method of claim 22 wherein the polymer precursor is converted to polymeric coating that is not subsequently removed from the substrate.
 24. A method of coating a wafer, comprising: dispensing at least one organic liquid on a first major surface of the wafer; spinning the wafer until the organic liquid is distributed across the wafer surface; dispensing a die coat composition on the wafer having solvent on its surface, wherein the die coat composition comprises at least one organic solvent; and spinning the wafer until the die coat composition is distributed across the wafer surface.
 25. The method of claim 24 wherein the die coat composition further comprises an additive selected from the group consisting of photoactive compounds, adhesion promoters, stabilizers, surfactants, and combinations thereof.
 26. The method of claim 24 wherein the die coat composition further comprises a polymer precursor selected from the group consisting of polyamic acid, polyamic ester, polybenzoxazole precursors, and combinations thereof.
 27. The method of claim 26 wherein the polymer precursor is converted to polymeric coating that is not subsequently removed from the substrate.
 28. A method of coating a wafer, comprising: dispensing at least one organic liquid on a first major surface of the wafer; spinning the wafer until the organic liquid is distributed across the wafer surface; dispensing a die coat composition on the wafer having solvent on its surface, wherein the die coat composition comprises an additive selected from the group consisting of photoactive compounds, adhesion promoters, stabilizers, surfactants, and combinations thereof; and spinning the wafer until the die coat composition is distributed across the wafer surface.
 29. The method of claim 28 wherein the organic liquid comprises an organic solvent.
 30. The method of claim 29 wherein the die coat composition further comprises at least one organic solvent.
 31. The method of claim 28 wherein the die coat composition further comprises a polymer precursor selected from the group consisting of polyamic acid, polyamic ester, polybenzoxazole precursors, and combinations thereof.
 32. The method of claim 31 wherein the polymer precursor is converted to polymeric coating that is not subsequently removed from the substrate.
 33. A method of coating a wafer, comprising: dispensing at least one organic solvent on a first major surface of the wafer; spinning the wafer until the solvent is distributed across the wafer surface; dispensing a die coat composition on the wafer having solvent on its surface; and spinning the wafer until the die coat composition is distributed across the wafer surface.
 34. A method of coating a wafer, comprising: dispensing at least one organic solvent on a first major surface of the wafer; spinning the wafer until the solvent is distributed across the wafer surface; dispensing a die coat composition on the wafer having solvent on its surface wherein the die coat composition comprises at least one polymer precursor; and spinning the wafer until the die coat composition is distributed across the wafer surface.
 35. A method of coating a substrate, comprising: dispensing at least one prewet solvent on a first major surface of the substrate; spinning the substrate to distribute the prewet solvent across the substrate surface; dispensing a die coat composition comprising at least one die coat composition solvent on the first major surface of the substrate having at least one prewet solvent thereon; spinning the substrate to distribute the die coat composition across the substrate surface; and dispensing an edge bead removal composition comprising at least one edge bead removal solvent on a second major surface of the substrate and the edge of the substrate to remove die coat composition present on the second major surface and the edge of the substrate; wherein at least one prewet solvent is the same as at least one die coat composition solvent and at least one edge bead removal solvent.
 36. The method of claim 35 wherein the edge bead removal composition is an edge bead removal solution.
 37. A method of coating a substrate, comprising: dispensing at least one organic liquid on a first major surface of the substrate; spinning the substrate to distribute the organic liquid across the substrate surface; dispensing a polymeric precursor composition on the substrate having organic liquid on its surface; and spinning the substrate to distribute the polymeric precursor composition across the substrate surface; wherein the polymeric precursor composition is converted to polymeric coating that is not subsequently removed from the substrate.
 38. A method of coating a wafer, comprising: incorporating an additional nozzle into a wafer processing machine; positioning the additional nozzle such that it is directed at the center of a wafer held in the wafer processing machine; causing the nozzle to dispense at least one organic solvent on the wafer by triggering a solenoid; spinning the wafer to distribute the organic solvent across the wafer surface; dispensing a die coat composition on the wafer having organic solvent on its surface; and spinning the wafer to distribute the die coat across the wafer surface.
 39. The method of claim 38 wherein the solvent has a vapor pressure of less than about 100 mm Hg at 20° C.
 40. A method of coating a wafer, comprising: incorporating an additional nozzle into a wafer processing machine; positioning the additional nozzle such that it is directed at the center of a wafer held in the wafer processing machine; causing the nozzle to dispense at least one organic solvent on the wafer by triggering a solenoid; spinning the wafer at least until the organic solvent is distributed across the wafer surface; dispensing a die coat composition on the wafer having organic solvent on its surface wherein the die coat composition comprises at least one polymer precursor; and spinning the wafer at least until the die coat is distributed across the wafer surface.
 41. A method of coating a wafer, comprising: dispensing at least one organic solvent on a first major surface of the wafer; spinning the wafer at least until the solvent is distributed across the wafer surface; dispensing a die coat composition on the wafer having solvent on its surface, wherein the die coat composition comprises at least one polymer precursor and at least one organic solvent; and spinning the wafer at least until the die coat composition is distributed across the wafer surface.
 42. The method of claim 41 wherein the wafer is a silicon wafer.
 43. The method of claim 41 wherein the step of dispensing a solvent comprises dispensing a solvent having a vapor pressure of less than about 100 mm Hg at 20° C. on the wafer.
 44. The method of claim 41 wherein the step of dispensing a solvent comprises: positioning a nozzle to dispense the solvent in the middle of the wafer; controlling the nozzle with a solenoid; and causing the nozzle to dispense the solvent by signaling the solenoid.
 45. The method of claim 41 wherein dispensing at least one organic solvent on the wafer comprises dispensing at least one solvent that is the same as the at least one solvent of the die coat composition.
 46. The method of claim 45 wherein the polymeric die coat is used in an amount less than the amount used under the same conditions without a solvent prewet step.
 47. The method of claim 41 further comprising heating the die coat composition to form a polymeric die coat.
 48. The method of claim 41 further comprising removing die coat composition from the edge of the wafer.
 49. The method of claim 41 further comprising removing die coat composition from a second major surface of the wafer.
 50. A method of coating a substrate, comprising: dispensing at least one organic liquid on a first major surface of the substrate; spinning the substrate to distribute the organic liquid across the substrate surface; dispensing a die coat composition on the substrate having organic liquid on its surface, wherein the die coat composition comprises at least one organic solvent; and spinning the substrate to distribute the die coat composition across the substrate surface.
 51. The method of claim 50 wherein the die coat composition further comprises an additive selected from the group consisting of photoactive compounds, adhesion promoters, stabilizers, surfactants, and combinations thereof.
 52. The method of claim 50 wherein the die coat composition further comprises a polymer precursor selected from the group consisting of polyamic acid, polyamic ester, polybenzoxazole precursors, and combinations thereof.
 53. The method of claim 52 wherein the polymer precursor is converted to polymeric coating that is not subsequently removed from the substrate.
 54. A method of coating a substrate, comprising: dispensing at least one organic liquid on a first major surface of the substrate; spinning the substrate at least until the organic liquid is distributed across the substrate surface; dispensing a die coat composition on the substrate having organic liquid on its surface, wherein the die coat composition comprises an additive selected from the group consisting of photoactive compounds, adhesion promoters, stabilizers, surfactants, and combinations thereof; and spinning the substrate at least until the die coat composition is distributed across the substrate surface.
 55. The method of claim 54 wherein the organic liquid comprises an organic solvent.
 56. The method of claim 55 wherein the die coat composition further comprises at least one organic solvent.
 57. The method of claim 54 wherein the die coat composition further comprises a polymer precursor selected from the group consisting of polyamic acid, polyamic ester, polybenzoxazole precursors, and combinations thereof.
 58. The method of claim 57 wherein the polymer precursor is converted to polymeric coating that is not subsequently removed from the substrate.
 59. A method of coating a wafer, comprising: dispensing at least one organic liquid on a first major surface of the wafer; spinning the wafer to distribute the organic liquid across the wafer surface; dispensing a die coat composition on the wafer having solvent on its surface, wherein the die coat composition comprises at least one organic solvent; and spinning the wafer to distribute the die coat composition across the wafer surface.
 60. The method of claim 59 wherein the die coat composition further comprises an additive selected from the group consisting of photoactive compounds, adhesion promoters, stabilizers, surfactants, and combinations thereof.
 61. The method of claim 59 wherein the die coat composition further comprises a polymer precursor selected from the group consisting of polyamic acid, polyamic ester, polybenzoxazole precursors, and combinations thereof.
 62. The method of claim 61 wherein the polymer precursor is converted to polymeric coating that is not subsequently removed from the wafer surface.
 63. A method of coating a wafer, comprising: dispensing at least one organic liquid on a first major surface of the wafer; spinning the wafer at least until the organic liquid is distributed across the wafer surface; dispensing a die coat composition on the wafer having solvent on its surface, wherein the die coat composition comprises an additive selected from the group consisting of photoactive compounds, adhesion promoters, stabilizers, surfactants, and combinations thereof; and spinning the wafer at least until the die coat composition is distributed across the wafer surface.
 64. The method of claim 63 wherein the organic liquid comprises an organic solvent.
 65. The method of claim 64 wherein the die coat composition further comprises at least one organic solvent.
 66. The method of claim 63 wherein the die coat composition further comprises a polymer precursor selected from the group consisting of polyamic acid, polyamic ester, polybenzoxazole precursors, and combinations thereof.
 67. The method of claim 66 wherein the polymer precursor is converted to polymeric coating that is not subsequently removed from the wafer surface.
 68. A method of coating a wafer, comprising: dispensing at least one organic solvent on a first major surface of the wafer; spinning the wafer to distribute the solvent across the wafer surface; dispensing a die coat composition on the wafer having solvent on its surface; and spinning the wafer to distribute the die coat composition across the wafer surface.
 69. A method of coating a wafer, comprising: dispensing at least one organic solvent on a first major surface of the wafer; spinning the wafer to distribute the solvent across the wafer surface; dispensing a die coat composition on the wafer having solvent on its surface wherein the die coat composition comprises at least one polymer precursor; and spinning the wafer to distribute the die coat composition across the wafer surface. 